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How was this old beacon used?
I saw this beacon at an old airport; how and in what situations was it used?

Please provide attribution for your image.

What airport was this seen at? Are there other pictures? Airport beacons are typically White/Green Rotating units and do not have a red light on top. This may however predate modern convention.

I took this pic myself at Ljungbyhed, Sweden(ESTL). More pics on request ;)

It's the airfield identification beacon.

An aerodrome beacon or rotating beacon is a beacon installed at an
  airport or aerodrome to indicate its location to aircraft pilots at
  night.
An aerodrome beacon is mounted on top of a towering structure, often a
  control tower, above other buildings of the airport. It produces
  flashes not unlike that of a lighthouse.
Airport and heliport beacons are designed in such a way to make them
  most effective from one to ten degrees above the horizon; however,
  they can be seen well above and below this peak spread. The beacon may
  be an omnidirectional flashing xenon strobe, or it may be an
  aerobeacon rotating at a constant speed which produces the visual
  effect of flashes at regular intervals. Flashes may be of just a
  single color, or of two alternating colors.

Flyer's version of a lighthouse... except it indicates the port, not a hazard to avoid. I've seen these from above, when in a friend's private plane after dark; they definitely do catch your eye and help you plan your approach.


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How do they fill fuel in big aircraft?
Being a passenger, I usually will have view from only one side of these planes and hence don't know if same thing is happening on other side of the plane. I have observed hoses connected to wings, but there are always many connections to plane when its on ground and never sure which one is for fueling.
Looking at the answers for fuel tank description here or here, when they are filling fuel, do they connect hoses to each tank individually or just connect to one tank? Or is it per side - fill up each side individually.
Also suge/vent tank at the tail end of a380 seems to too high. Do they fill in those tanks too?
After fuel calculations are done, is there a standard fuel distribution that has to be done to every tank for weight/balance reasons?

when they are filling fuel, do they connect hoses to each tank individually or just connect to one tank? Or is it per side - fill up each side individually.

They typically connect to a fueling duct that connects to all tanks. The details vary for different aircraft makes, but a typical arrangement is to have a fueling console next to an under-wing fueling port. The console has a gauge for each tank and switching that allows the fueler to open valving that will allow fuel into each tank from the pressurized fueling duct until the tank is filled to the desired level. Some aircraft will have two fueling ports—one under each wing—that will allow fueling from a second source simultaneously, but they both feed the one pressurized duct.
There is no standard fuel distribution scheme that works across all aircraft models. However, there is great similarity in how it's done, and typically for the same model of aircraft, the tanks will be filled per the same schedule almost every time for a given amount of fuel.

is there a standard fuel distribution that has to be done to every tank for weight/balance reasons?

That it be done right is critical for proper weight & balance, and sometimes fuel is used for balance purposes. For example, let's say you had a tail-heavy load in a 747 freighter such that the zero fuel weight c.g. exceeded the aft limit. If you put fuel in the center tank and consider that fuel as ballast, you could bring the zero fuel weight c.g. within the limit since the 747 center tank c.g. is the most forward of the 747 tanks. And, of course, you have to be careful to not burn that ballast fuel.
If you want to explore fuel loading on a 747-400, go to 747.terryliittschwager.com, select the first aircraft, N402YY, and give it fuel.

that site is very interesting. Will play with it

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How is it safe and legal to land in parallel runways
How come it is safe and legal to land in parallel runways (for example, in SFO).
The planes are way too close, at a distance that would not, I assume, be according to flight regulations and safety rules during cruise flight.
At what distance from airport or below what altitude becomes it ok to fly like this?
Can airplanes also take off in parallel, or only land?

also related: http://aviation.stackexchange.com/questions/9361 http://aviation.stackexchange.com/questions/3649

Frankly, you could make a decent argument that SFO's parallel runway operation isn't particularly safe. It's not like the FAA set criteria for SOIA and parallel visual approaches and SFO was built to match those requirements; SFO was built with runways 750' apart and the rules were set based on that. But safety is not a yes/no question, it's a matter of degree. We've all decided to accept the additional risk, which is managed through special procedures and training, in exchange for allowing SFO to handle a reasonable volume of traffic (since building an additional runway is near-impossible).

Simultaneous Independent and Dependent Parallel Instrument Approaches - 6.2.2 Target Level of Safety : "The target level of safety (TLS) used for simultaneous approaches was no more than one fatal accident per 25 million approaches"

Not a duplicate: "is this practice safe/wise" is a different question than "what is the regulatory minimum distance." Voting to reopen.

I agree, this is a different question and not a duplicate. I’d like to re open as well.

Whether Parallel Runway Operations are allowed at an airport is dependent on many factors, such as:

Proximity of runways to each other
Availability of precision approach systems for each runway

There is two modes that are interesting here, which is the full parallel mode, where lateral separation is no longer required once both aircraft are established in the precision approach and staggered mode, where the runways are too close for parallel mode and need to maintain 2.5 NM lateral separation during the approach phase.
The same regulations apply to departures, you can read about it in EUROCONTROL's SkyBrary.
Related questions:
How are go-arounds safe with parallel runways?

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How big can a pulsejet be?
Pulsejets are mostly known for propelling the V-1 flying bomb, and have some use as small remote-controlled plane engines. In either case, the pulsejets aren't particularly big, as far as jet engines go.
How big can a puslejet be realistically made? Assuming that, for some reason, there was a need to power a much bigger plane with pulsejets, at which point would it stop making sense to make the pulsejet bigger, and use multiple smaller pulsejets?

At the point where the structural rigidity needed to overcome the vibration of a single enormous pulse train becomes so heavy that the aircraft can't fly anymore, replace the single large pulsejet with several smaller ones, whose individual pulses are smaller.
Conversely, imagine replacing a car's V8 engine with a single-cylinder engine of the same power.  It would need much stronger engine mounts, flywheel, clutch, transmission, etc.  (Single-cylinder car engines weren't that rare a century ago; good luck finding one today.)
But the main reason that large pulse jets are rare is their low fuel efficiency.  The bigger the engine, the more that matters.
See also: What are the pros and cons of a pulsejet?

The bigger the pulse jet, the combustion becomes lower frequency but much great power per pulse. So it generates low frequency of very loud pulses, which in turn causes low frequency of high amplitude vibrations. If you are planning to mount it on airplane, it's airframe should be very strong. And unlike continuous jet engines, pulse jet thrust to weight ratio may become constant or decrease with scale because combustion pulse rate/frequencies decrease. So it's not advantageous to use single big pulse jet. Better go with small or medium pulsejets but multiple of them.

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Can an unserviceable component be fitted on a serviceable aircraft for a maintenance check?
I was doing some reading on aviation regulations and I wanted to understand from an expert whether the following situation is allowable or not. I have reviewed EASA continuing-airworthiness guidelines but am still unclear as this is a bit of a unique scenario.
Appreciate if you can shed some light on whether this situation is permissible or not.

A component fails and is removed from Aircraft A and declared unserviceable (with an "unserviceable" tag).
A similar component is removed, via robbery/cannibalisation, from another aircraft (Aircraft B) undergoing maintenance activity (A or C check), and provided to Aircraft C, which has a similar failure.
There is now a "hole" in Aircraft B, since the component has been robbed/cannibalised to support Aircraft C for the latter's maintenance requirement.
The original failed component (from Aircraft A) which was declared unserviceable (with an "unserviceable" tag) will be used to support the maintenance check inspections/tests for Aircraft B.
These tests are to inspect/test aircraft systems, and the "hole" needs to be plugged to carry those out.
The unserviceable component will eventually be removed from Aircraft B as unserviceable (with the "unserviceable" tag).

On the one hand, all that matters is what parts are attached to the airplane when the maintenance release is signed.  On the other hand, if you are performing a functional check to meet an MSG-3 system performance requirement for a particular system, all of the components of that system have to be the ones the aircraft will go into service with, so in that case you couldn't install a technically unserviceable part to make it work if the unserviceable part was involved in producing the performance being tested.

Thanks John, so basically as long as it is not used to sign off a task it should be okay. But if it's used simply to fill a hole then it's acceptable. Are there any regulatory documents that can be referred or add more background on such matters.

Sorry not I'm not aware of any, which is why I didn't post it as an answer.Logically, the configuration of the a/c is not important prior to something being signed off, except where configuration item directly impacts the test being signed off, and when the whole a/c is signed off, it's in the proper airworthy configuration.However, if you are in the US, you might be prudent to run it by the local FAA Primary Maintenance Inspector before proceeding.The answer you get may vary from PMI to PMI. I was OEM support engineering in the Regional business, and we were aware of large policy variations.

@JohnK OP mentions EASA in the post, so the FAA is probably irrelevant here. :) (Though it does have both FAA and EASA regulation tags, so it's a bit confusing.)

@JohnK thanks for your feedback, I think it is fair that you have posted this as a comment. Either way, it does help me. I might have to speak to a representative to get a more granular and specific answer to my situation.

@FreeMan My apologies, I did want to refer to EASA and FAA both since there is alignment across many of the Regulations, GMs, AMCs, etc.

The US environment is funny that way. With these grey area issues it often comes down to the judgement of the local PMI and FAA Regional Office policy. In some regions they are very sticky, not so much in others.  Some Regional Airlines had lots of leeway to do their own in-house mods, others couldn't do a thing without an OEM service bulletin.

@JohnK Cheers, I have noticed that too. I think in this case, we will err on the side of caution and avoid utilising this U/S spare on an A/C undergoing a check. Appreciate all your feedback.

EASA Regulations do not specifically preclude you from doing what you are planning to. They leave an awful lot of room for interpretation. How you do your maintenance is up to you, as long as you meet the core requirements and that your processes can be audited.
Additional rules for this type of activity would normally covered by a local procedure (such as Robbery). If you do not have a covering procedure internally then you should absolutely be checking with your Quality Assurance department to validate your actions before undertaking the procedure.

Welcome to [aviation.se]. Please take the [tour] and read through the [help], specifically the section on answering. You'll find that this is a Question & Answer forum, not a general discussion board, and as such, we're looking for detailed and specific answers whenever possible. "...may not..." isn't the sort of specific answer we're looking for. Please feel free to [edit] your answer to include specific notes in the regulations or decisions issued that would allow this, in order to back up your claims.

Thank you, although the scenario is a bit too specific to garner a targeted response. I will choose to accept your answer as fair considering that local procedures must be referred to and that is something we may need to evaluate internally.


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Radar fuel level sensor
Do any aircraft use radar to measure the level of fuel in their fuel tanks?

Aside from whether it would work or not (I have no idea) it seems that there are plenty of far simpler (= less expensive) ways to measure fuel quantity.

But why?????????

I use radar TLI's in many industrial/marine control systems but I'm not sure it would work in aircraft. Big problem is that they can't measure close to the sensor so they require a "hat" to offset them from the top of the tank.

I've never heard of that kind of thing in aircraft in 40 years in the industry. Capacitance tubes are simple, very accurate, and solid state, that is, no moving parts, and work perfectly well, so there isn't really a need to go with a completely different technology.

Capacitance tubes work in space too. (see answers to Remaining fuel estimation/measuring Strategy in a spacecraft)


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What does the correlation between weather and midair collisions tell us?
The FAA's AFH states that "most midair collision accidents occur in good weather", in daylight, and nearby airports/navigation aids. What does this imply?
(One obvious explanation to this fact could be that there is simply much more traffic in this conditions, and despite a much lower accident rate per flight hour there are more overall accidents.)

Your obvious explanation sounds very reasonable to me, even if correlation isn't an explanation as such. I'm not sure what your actual question is here, are you looking for sources or studies that analyze this topic?

I would say it is because in bad weather everyone is in ifr. Mid-airs are more a vfr phenomenon

Near airports/navaids makes sense because those are destinations (either initial/final or intermediate as a waypoint). It mostly implies that airplanes are hard to see, something ADS-B and Nexgen are helping to avoid. My aircraft makes audible call-outs if I get too near an ADS-B or other interrogation target, as a feature of our Garmin GTX-345 which is integrated into our comms panel.

@Pondlife I'm trying to understand if there is a causal connection, e.g. complacency in good conditions leading to more accidents, or merely correlation that has no practical implications.

Is it possible/reasonable/common to be flying in IMC without being under ATC? Is it legal to run canyons (say the Coalville-Heber-Sandy route) in the soup, entirely with GPS and good maps, like Ramius did in "Hunt for Red October" ( but with a sub)?

In poor weather there are apt to be less VFR aircraft and more IFR. IFR are required to participate with ATC and automatically receive separation by time, altitude, and radar (when available). VFR do not require any separation and are not required to participate with ATC. There are also more flights in VFR weather than there are with IFR.
I might get flamed for this, but in general a IFR pilot is more proficient than a VFR pilot. The medical (commercial opps), testing, and currency requirements for a IFR license are usually considerably more complex than VFR - meaning (admittedly there are exceptions i.e. aerobatic pilots) IFR pilots are generally more proficient.
The following added in response to comments below
According to the FAA, "...  the majority happen within five miles of an airport" https://www.faasafety.gov/gslac/alc/libview_normal.aspx?id=6851. So, cruise environment is not a factor, and IFR have ATC separation at all times, making this predominantly a VFR landing/takeoff problem. Most IFR flights are commercial requiring a 6mo medical where as private VFR pilots require 2yrs or LSA and Ultralight do not require a aviation medical. (The private medical requirements just changed, but this discussion is based on prior years data.)
In addition to excersize IFR privileges, a pilot must remain current every 6mo where as a VFR pilot does not (except for night landings).
IFR flights will have a higher percentage of two man crews compared to most VFR flights with a single pilot. The extra set of eyes is extremely significant particularly during the landing/takeoff phase of flight.

That's plausible, but would not be valid if collisions occur at FL300. It would be good to eliminate other possibilities with more details about the circumstances of the collisions.

I'm not sure what you mean by the "medical (commercial opps) ... for an IFR license"? At least in the US, there are no extra medical requirements for an instrument rating, and you don't need to have a commercial certificate either.

And of course, nothing (assuming that the pilot has an instrument rating) prevents a pilot from electing to fly IFR in VMC. It is only the combination VFR in IMC that is prohibited. (The other two possibilities, VFR in VMC and IFR in IMC, are obviously allowed.) If a VFR flight transitions from VMC to IMC, then the pilot must either transition to IFR or get back into VMC.


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An-225 antenna layout
Does anyone have a good reference or information about the antenna layout on the An-225?
Particularly interested whether the VOR antennas are up on the V-Stabs, or somewhere more creative.
Thanks in advance.


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What do the various lights in the overhead aisle light cluster of a Bombardier Q400 NextGen represent?
I took this picture of an overhead aisle light cluster in a Bombardier Q400 NextGen.

Copyright: self
I am inquiring about the role of the bottom row of six rectangular lights. From right to left they are yellow, dark blue, dark red, green, orange, and medium red.
My observation regarding these lights:

The seatbelt light, when lit (and accompanied by a single ping), lights up the green light, for about five seconds.
A double ping, with the second ping at a lower frequency than the first ping, lights up the medium red light, for about five seconds.

I presume that these six lights are intended for communicating with cabin crew. I would like to know the detailed meaning of these lights.

Related: What are these five indicators at the front of the 737 passenger cabin? and What does a blue light by the toilet sign mean?. This question is bound to a high score :-) The top sign probably means going to the toilets in group is prohibited.

This is the so called "area call panel" and it is indeed used to signal the cabin crew. The colours and their respective meaning is not regulated and depends on the aircraft and aircraft manufacturer.
A selection of colors, manufacturer and type according to airliners:

Boeing / McDonnell Douglas:

Pink - Flight crew to FA call ORFA to FA call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Red (717 only) - Lavatory smoke detector set off
Green (DC-9 only) - Unused, included as a placeholder for an unknown function.

Airbus:

Red - Flight crew to FA call OR (some aircraft only) FA to FA
call
Blue - Call to FA from passenger in seat
Amber - Call to FA from passenger in lavatory
Flashing Amber - Lavatory smoke detector set off
Green (some aircraft only) - FA to FA call

Further down you can read, that Bombardier Dash 8 uses solid green for a regular call and flashing amber for emergency call.
A definitive answer can only be found in the respective aircraft or crew manual.


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Is it possible to be a pilot for both the RAF and a Commercial company?
I have always wanted to be a pilot for both the RAF and Commercial airlines.
Would it be possible for me to serve, for say 6 months in the RAF, and then when not deployed work as a commercial pilot. Just asking this as I saw a video a few months ago of a US Air Force member who works for United when he is not working for the USAF.
Thanks - Jay.

What you probably saw was an Air Force Reserve pilot working for United, active duty cannot hold another job.

I agree it was probably a reservist, but active duty military members may hold another job, it just cannot conflict with military duties. Flying for a commercial airline would likely not work out, but I have known several people who worked as CFIs on the side.

Ok, thank you for this information, I was just interested.

I expect the  Royal Air Force Reserves would consider someone who is already qualified for the aircraft.   Most likely someone who has just left the full time RAF with transport experience.

Basic officer training in the RAF takes 30 weeks, so you're already over your six months, even before you start pilot training.
When you sign up you enlist for a minimum period which varies according to your speciality. Six to twelve years is typical.
Source
Assuming you get through pilot training and make it to a squadron, you're not going to just sit around and wait for a war. There's ongoing training, exercises, active deployments and other duties that will take up your time. Whilst there will be periods where your working life will be 9-to-5, there will also be periods where you'll be working nights, weekends, public holidays, and away from home.
I don't know what the RAF policy on second jobs is, but for practical reasons I can't see that you would be able to drive buses for easyJet or the like.

As noted by Ron Beyer in a comment above, it is technically allowable for any member of the UK armed forces to have a second job, but it must not conflict with the requirements of their service, which makes anything other than a hobby-job completely impracticable. Even during time-off, there are various levels of requirement to remain available.


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What is the most cost effective way of combining an instrument and multi engine check ride?
I have a single engine land commercial without an instrument rating. I am currently completing the instrument rating. Now if I need a single engine and multi engine commercial with instrument ratings, what would be the most cost effective way of going about this?

Can we assume you're asking about the US?

The cheapest way (I'm talking Canada here) is to do the basic instrument training in the single, then do the multi rating and check ride separately, then the do some practice approaches and emergencies in the twin and multi simulator to prepare for the multi-IFR checkride , and do that.  There's no point in doing an SE check ride.  When I did it some years ago I bit the bullet and did almost of the air time in a Seminole because I was uncomfortable with going into a multi-IFR checkride with maybe only 15 hours in the twin, and the kind of sims available today didn't exist.
Go to a school that has one of those Red Bird motion simulators or equivalent and take maximum advantage of the portion of the training that can be in a sim.  That'll save a ton of money.
Also use MS Flight Sim or Xplane to practice practice practice at home.  It is a very powerful tool if used properly.  By "properly" I man make sure the stuff you practice on your own is being correctly done, and are not reinforcing incorrect stuff.

Oops I got caught out assuming US rules were similar to Canadian ones again.  Yes, my description is based on Canadian rules where there are 3 instrument rating groups, 1 (multi), 2 (multi-centerline thrust) and 3 (single), and for a 1 you have to do the checkride in a twin.  Good catch. Thanks.

So how would Transport Canada go about converting someone who holds a CPL ASEL, AMEL & IA to the equivalent in Canada?

Not sure.  If it's just a paperwork exercise, I think it would be no issue to get a Group 1 if you have an FAA instrument rating and an FAA multi rating together.  If a checkride is required however, you would have to do it in a twin to make it a Group 1.


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What do the green, white and yellow bands mean on an airspeed indicator?

what are these  green and white and yellow bands in the Airspeed Indicator use for ?

The FAA has a nice introduction document on flight instruments, which explains all the standard markings on a typical airspeed indicator (ASI):

As shown in [the figure above], ASIs on single-engine small aircraft
  include the following standard color-coded markings:

White arc—commonly referred to as the flap operating
  range since its lower limit represents the full flap stall
  speed and its upper limit provides the maximum flap
  speed. Approaches and landings are usually flown at
  speeds within the white arc.
Lower limit of white arc (VS0)—the stalling speed
  or the minimum steady flight speed in the landing
  configuration. In small aircraft, this is the power-off
  stall speed at the maximum landing weight in the
  landing configuration (gear and flaps down).
Upper limit of the white arc (VFE)—the maximum
  speed with the flaps extended.
Green arc—the normal operating range of the aircraft.
  Most flying occurs within this range.
Lower limit of green arc (VS1)—the stalling speed
  or the minimum steady flight speed obtained in a
  specified configuration. For most aircraft, this is the
  power-off stall speed at the maximum takeoff weight
  in the clean configuration (gear up, if retractable, and
  flaps up).
Upper limit of green arc (VN0)—the maximum
  structural cruising speed. Do not exceed this speed
  except in smooth air.
Yellow arc—caution range. Fly within this range only
  in smooth air and then only with caution.
Red line (VNE)—never exceed speed. Operating above
  this speed is prohibited since it may result in damage
  or structural failure.

(FAA Handbook - Chapter 8 - Flight Instruments, emphasis mine)

Wikipedia has a very fine article of this subject, and by chance(?) it has the picture you posted in your question. To save the trouble of going there to check this stuff out, I've composed a simplified explanation of the markings:
(as I was writing this, Bianfable posted a much better answer, but I just could not let my effort go to waste, so I posted this anyway :)
From 0 to 250 the coloured arcs on the dial mean:
60 - beginning of the white arc:

flaps extended stall speed, this is the minimum speed you can fly with this plane with flaps extended (= out = down).
the white arc marks the speed range you can use the flaps within

65 - beginning of the green arc:

stall speed with flaps retracted, this is the minimum speed you can fly this plane when flaps are retracted (= up).
the green arc marks the speed range you can normally fly the plane in

100 - end of white arc:

maximum flaps extended speed, this is the fastest you can go with flaps down. If you go faster, you risk damaging the flaps or the system that moves them.

165 - end of green arc, beginning of yellow arc:

maximum cruising speed, this is the fastest you can safely fly this plane (with flaps retracted of course).
the yellow arc marks the speed range within which you can operate the plane with caution, in smooth non turbulent air and without making sudden movements of the controls. Not recommended unless you really know what you are doing.

208 - red line,end of yellow arc:

Never exeed speed, do not go faster or you will break the plane and kill yourself!

"do not go faster or you will break the plane and kill yourself!" Isn't it more of a "warranty void above this speed" thing? Just because the aircraft is unrated in that region and it being a bad idea to go there, doesn't mean you'll get killed. Risk of death doesn't equal death.

Strictly speaking you are correct @Mast , the question however is obviously of the absolute beginner level, so I took the liberty of exaggerating on the safer side of things. A beginner pilot, when flying past the redline is in imminent risk of death. Sudden and large control deflections can easily break up or seriously damage an airframe, and very few beginner pilots have silky smooth touch...

@Jpe61 I've just found this question as an instructor under training for FI(S)! Also, beginner or otherwise, anyone who's going to be flying beyond VA ought to know what to do when facing a situation where they can't avoid busting VNE without busting G-limits. Instilling the idea that both "will" break the aircraft apart isn't exactly helpful.

Congrats on your future FI(S)! As I stated above, the question is very, very, very basic. Such questions certainly deserve an answer, I've decided my answer will also be very, very, very basic (some here  downvote or vote to close basic questions rather than bothering to answer, not me (usually)). By the time an aspiring pilot gets to control a plane, the V's surely have been properly introduced.


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What Is This in The Top of IL-86VKP?
What Is This in The Top of IL-86VKP?

It's an oxygen chamber to keep the exalted leader looking artificially young...

Ilyushin Il-80

Source: Wikipedia
The "canoe" is thought to house "advanced" satellite communications equipment. This is a classified aircraft though, so there isn't a lot of publicly available information on exactly what other equipment might be contained in that hump.

This angle makes that a shockingly unaerodynamic looking hump! It looks like the front is very vertical and not at all smoothly blended into the roof line. Of course, that's topic for a different question, and considering the classified nature of the aircraft, probably an unanswerable one, so I won't bother asking

@FreeMan Side-on angles may be deceiving. It looks like the front is tapered to cause less drag so it probably isn't a huge impact. It doesn't seem to matter though, the aircraft can stay airborne indefinitely because there seems to be a refueling probe on the nose.

Good thing about refuling, too, @RonBeyer - those look like very inefficient low-bypass engines! </OT ramblings>


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Why does pulling the mixture to idle cutoff increase the RPM slightly?
When adjusting fuel control on a reciprocating engine, why is there a slight RPM rise (50-RPM rise) when pulling the mixture control to idle cutoff? Why if more than a 50-RPM rise, carburetor is set too rich?

Engine are usually run slightly richer than a stoichiometric mixture, to ensure reliable running and avoid overheating the pistons and valves. When you cut off the fuel, it goes from slightly too much fuel to none - and so it's briefly at a stoichiometric ratio.
The engine runs slightly faster at this ratio because it's not wasting energy heating up unburnt fuel.
If you see more than a 50rpm rise, it was previously running further from stoichiometric than necessary (as determined by the engine manufacturer, and many years of experience), reducing power and wasting fuel.

The richer mixture isn't really necessary for cooling at idle the way it is at higher power settings; it's more to do with cold starts in the absence of a choke, as I said in my own post.  Otherwise your post is fine.

The idle circuit is set to be richer than necessary to help the engine run better when cold.  This is because you start with prime, not a choke, so there is nothing to keep the mixture extra rich for cold running once the primer fuel in the intake has been used up.
If you don't set the idle mixture richer than necessary, the engine will die after running a few seconds at minimum idle without extra prime, unless you immediately wind the RPM up to above 1000, which is not really good on a cold engine that is just starting to get oil circulation going (I keep RPM as low as possible until there is significant oil pressure showing to indicate the main bearings are being pressurized and the cam lobes are getting splashed).  The alternative is to pump the throttle to squirt fuel from the accelerator pump, or keep slowly stroking the primer to keep it running until the oil pressure is fully up and you can raise the idle RPM.
So as Robin's answer mentions, the mixture passes briefly through stoichiometric, or close to its "best power" idle mixture range as it continues to no fuel at all, causing the RPM rise.
On Marvel Schebler carburetors, there is finger screw knob at the back of the carb body below the float bowl that moves the idle jet in and out.  You can reach in and turn it with your fingers.  You set this knob by trial and error until you get the (roughly) 50 RPM bump in RPM when going to idle cutoff.
Some private owners will set the idle mixture at a more lean setting, to reduce lead fouling of spark plugs, without having to fuss with the mixture every time the throttle is at idle. The problem with this is, as mentioned, it's harder to keep it running on a cold morning.
My own homebuilt, with a Lycoming O-290, was set like this by the previous owner when I bought it, which I figured out after pondering why there was no RPM rise at idle cutoff, and why I needed to keep adding prime after starting on a cold day.  Since I run on auto fuel now and lead fouling is no longer an issue I've restored the normal rich idle setting.


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Is it possible for the Boeing 737NG to do a powerback?
I'm curious, in a non-normal situation, where it's not possible to use a pushback tug, would it be POSSIBLE to perform a powerback on the 737NG, assuming the area was reasonably clear of FOD?

Maybe soon everyone will have these...

Possible? Yes! But not recommended.
There is nothing technical that would stop you from doing it. Thrust Reversers can be selected any time on the ground and there is enough thrust available to move the aircraft backwards. It is also not technically prohibited to do so:

Reverse Thrust
Intentional selection of reverse thrust in flight is prohibited.

(Boeing 737 NG FCOMv1 L.10.8 - Limitations - Operating Limitations)
There is nothing mentioned here that would prohibit the use of thrust reversers to back the aircraft. For comparison, on the Boeing 747 it is prohibited:

Reverse Thrust
Intentional selection of reverse thrust in flight is prohibited.
Backing the airplane with use of reverse thrust is prohibited.

(Boeing 747-400 FCOMv1 L.10.7 - Limitations - Operating Limitations)
Boeing does however not recommend using it on the 737 NG:

Backing with Reverse Thrust
Backing with reverse thrust is not recommended.

(Boeing 737 NG FCTM 2.4 - Ground Operations)
That is all the training manual has to say about it.

I do not know if backing with reverse thrust is actually done anywhere in a 737 NG. It was for sure done in older 737-100/-200 models:

When I flew the B737-200, we were trained in powerbacks, with SOPs set out, but it was to be used only as a last resort. I did only two during my time on the B737. On both occasions, we arrived in the US in a gravel equipped B737 that had a different nose wheel and their tow-bar would not fit.

(airliners.net)
It is also still being done in Boeing 757s:

(YouTube)

Thanks! I think it's kind of weird that it's prohibited on the 747 but not the 737! Of course, it's not recommended, but it IS still possible. Would you be able to refer me to the Southwest 737-700 FCOM? I can't find it and I'm sure it's full of cool stuff like this.

@MD88Fan It is definitely weird, I checked some other Boeing FCOMs: It is also prohibited for the 777, but not for the 767. For the 757 the FCOM I have says it is prohibited with P&W engines, but not with RR engines. Unfortunately I cannot tell you how to find the FCOMs. The ones I have, I purchased legally as part of simulations. But Google might be able to find some...

Is that an implication that the RR engine is more robust and less FOD sensitive than the PW engine? :)

@FreeMan Possible. Or P&W legal department was clever enough to prohibit it in the first place to avoid any liability and RR didn't :D To be honest, the engines are probably quite similar. Although the RR one is a three spool design which implies the fan can run slower, maybe that has something to do with it, maybe not...

There was a fair bit of sarcasm and marketing BS implied in my comment...

FOD is not the whole problem. I remember a weird problem with a particular airline, which was the only operator of a particular aircraft/engine type which had repeated issues with a spline joint in one of the jet engine rotors wearing to the point of being dangerously weak. After literally years of head-scratching, we discovered they were the only operator that routinely used reverse thrust to push back. (Names and model numbers intentionally redacted - but this happened about 25 years ago so it's no longer a live safety issue).

@MD88Fan For most of its life each 737 variant has only had a single engine type. The 747 program was launched with engine options from all three engine manufacturers, and that fact alone caused a lot of problems with the initial design. It's no big surprise the operating restrictions on the 747 were/are more restrictive.

"Possible" as in, "last flight out of Saigon, we'll try anything because the alternative is worse," maybe. But Boeing doesn't publish any procedure for it, as far as I've ever seen, and they generally take a very dim view of using T/R's at low speed. It isn't in any published non-normal procedures.
I've also heard, anecdotally, of one crew that tried it with a 737-200 freighter, who got a dramatic compressor stall (and a serious chewing-out later) out of the deal.
Short of mortars falling on the airfield, I doubt I'd consider operating that far outside published guidance.

Without the OpSpec, the airline won't do it even if the airplane is approved for it. But if the manufacturer hasn't approved the airplane for it first, the OpSpec won't happen.  I see no indications that Boeing ever approved the NG or Max for powerback ops, but I can't recall seeing it specifically prohibited from Boeing, either.


text:
For maximum glide range, should I minimize glide angle or AoA?
I'm currently taking an aeronautical engineering course in school. For an upcoming project, we're going to build balsa toss gliders and we have to design our own wings. The program we're using (Aery32) provides information about how the model will fly, including CoD, AoA, and glide angle. I already know that using long, tapered wings will provide the most efficiency, however, to further optimize the design, I need to know which item I should minimize- AoA or glide angle. Obviously in a perfect world I would do both however I don't have a large amount of time. To summarize- I'd like to know if reducing the angle of attack or decreasing the glide angle will provide a further glide.

Depends on what you are doing for your design. Is the aim to produce an aerofoil that can glide or an aerofoil that can perform well.

To clarify- the aim here is to fly the furthest distance. It will be thrown both from ground level (arm level, really) and from a high point. The wing will be a flat piece of balsa. I'm more concerned with the overall planform- is pursuing a high aspect ratio the correct move here, or does that not apply to aircraft of this scale (roughly 36 inch wingspan)? Thanks to everyone for your help.

The furthest glide is by definition the lowest glide angle! So if that is one of your design inputs, you should definitely go for that.

But seriously, reducing weight and form drag gets you the furthest.
1. General glide distance theory
With glide angle $\bar\gamma$ = -$\gamma$:
$\quad C_D \cdot \frac{1}{2} \rho V^2 \cdot S = W \cdot \text{sin }\bar\gamma \tag{1}$
$\quad C_L \cdot \frac{1}{2} \rho V^2 \cdot S = W \cdot\text{cos }\bar\gamma \tag{2}$
Division yields: tan $\bar\gamma$ = $C_D/C_L$, and both $C_D$ and $C_L$ are a direct function of Angle of Attack.
For the drag coefficient the following parabolic approximation can be used to incorporate induced drag: $$C_D = C_{D_0} + \frac {C_L^2}{\pi A e}$$ Minimal $\bar\gamma$ will be at maximal $C_L/C_D$, which will be found at $\frac{1}{2} \sqrt{\frac{\pi A e}{C_{D0}}}$. For the lowest glide angle, find the lowest form drag factor $C_D$ and the highest wing aspect ratio A. Longer span & narrower chord will get you further.
2. Toss glider particulars.
They Take Off by an arms throw, and upon release are thrown up with a lot of excess speed and let it exchange speed for extra altitude. After which the glide starts into the trimmed state:  speed, AoA and $\bar\gamma$ (thx to @Zeus for pointing this out).
 The graph above is from Low Speed Airfoil Data by M. Selig, page 68, and depicts $C_L, C_D$ and $\alpha$ at very low design Reynolds numbers. As can be seen:

$({c_l/c_d})_{max}$ of the wing profile, at Re > 300,000, occurs at $\alpha$ = 1°. So wing AoA should be kept close to this angle in flight.
The trimmed speed must be such that Re > 300,000 to reach the minimum $c_d$ at $c_l$ = 0.6. From this Re follows the wing chord, and from equation (2) above then follows $$V_{launch} = \sqrt{\frac{2W}{C_L \rho S}}  \tag{3}$$

Weight follows from the maximum energy W/S should be chosen such that it follows from a comfortable throw.

Reducing drag, yes.  Reducing weight?  Not sure, especially with smaller models and slower speeds.  Might be some more viscous effects going on.  But weight can be easily added or removed.

Weight (better yet: mass) is what (indirectly) propells the glider forward. See it this way: The more mass the glider has, the more energy you can launch it with, given a fixed launch speed. Therefore, your advice is poor. It's not about maximum payload (the case where mass savings are important), but maximum glide angle.

The Reynolds number chart is better advice. Re = Chord x Velocity x 100,000 /1.5 (units in meters and seconds).  The albatross, at 16 m/s, benefits from lower drag for a given lift than slower gliders.

"Upon release must be in their optimum flight state immediately". That's very academic. In reality (and particularly in competitions), you throw the glider up with a lot of excess speed, and let it exchange speed for extra altitude. This is one more thing that favours heavier models. And however you throw it, it will settle on the trimmed AoA and will "choose" the speed accordingly.

Well, well, well.  Time to go to ... the well.
"Balsa toss gliders" can be a lot of things, but they are a great place to start.  If they are thrown for distance design criteria will be different from flown from a height such as from a hill or tall building.
Reynolds number is a very important consideration for slow glider models.  No, they are not replicas of larger full scale gliders.  Studying lift to drag graphs at airfoiltools.com should get you off to a good start on selection of airfoil and AoA to use.
Design.  The Wright Brothers?  They started with kites, essentially tethered free flight models.  Airfoil in the back, flat plate in the front. Why??  Above a certain airspeed the cambered airfoil begins to generate a stronger suction peak above the wing forcing the nose down, reducing AoA$^2$.
Though their "canard" design made stall recovery more difficult$^1$, it makes the aircraft less likely to pitch up and stall due to a gust!.  So ... for both applications (throw and hill) ... unsweep Suzanne's$^3$ wings! ... or perhaps ... the "F-14" Suzanne (swing wing with canards).
As with all wings, optimal Lift/Drag AoA will give you optimal range, or Vbg.  Practice will make perfect here, as proper aspect ratio and drag reduction are needed to take 1st prize.  Strength, stability and crosswind performance are important too.
Before you jump into the build, do some homework on similarly sized gliders.  Good luck.
$^1$ The Wrights led the aviation world when sustained powered flight and turning a circle were state of the art.  Once aviators "went vertical":  climbing with more powerful engines, difficulties recovering from the "power on stall" doomed their design, opening the way for the classic tractor/rear tail design we see today.
$^2$  The upper wing suction peak strengthens as velocity increases. This is why Lift/Drag ratio improves with higher Reynolds number.
$^3$  Suzanne is the "Paper Airplane Guy's" record throwing design.


text:
What’s the difference between the MD 500E and MD 530F helicopters?
What’s the difference between the MD 500E and MD 530F helicopters? They look almost the same outwardly, and I can’t tell the difference. I would assume parts of the 530F are more modern, but what changed, specifically?

The MD530F is the lift version, designed for hot and high operations. It is fitted with a Rolls-Royce 250-C30 turboshaft engine and has slightly larger diameter rotors and a higher power transmission. A cargo hook kit can be fitted to lift 2,000lb (907kg) external loads.


text:
How much water does a passenger airliner carry?
How is the amount of water for (a) toilet and (b) drinking to be carried by a flight calculated in the industry? Is there any formula or thumb rule using which we can roughly estimate the amount of water required for toilet and for drinking calculated if the aircraft type $A$ is known and the flight has $P$ passengers on board and is scheduled to fly for $H$ before its next landing?

And not just water - other drinks are also served; water, juices, sodas, alchohol, coffee, tea.

Drinking water is almost never carried in the tanks, it would make people sick. Are you really asking how much bottled water/drinks the aircraft carries in the galley?

@Ron It's common sense isn't it and I don't think I need to mention that drinking water is carried in bottles. To answer you question, I am interested only in the quantity of (a) toilet water and (b) drinking water regardless of how it is carried.

@WrightBrother Maybe, maybe not. There are potable water tanks on larger aircraft (for use with hand-washing, etc), it isn't common sense that you don't want to drink from potable water tanks (potable water means drinkable). Airlines have gotten people sick from serving coffee made from the potable tanks, only recently did they switch to using bottled water for that.

Pls don't complicate it. I am only interested in the quantity of water. Nothing else! Assume that I know everything except the quantity. 100L in 50 bottles of 2 L each or 10 bottles of 10L each or in a big 100L bucket is irrelevant in this question. What is relevant is - should we carry 100L or 150L or 200L.

@RonBeyer  Long-haul carriers do provide water from the aircraft for drinking. Carrying enough bottled water for large, long flights is impractical. And no airline I know of uses bottled water for coffee. The coffee markers are plumbed in.

Operationally speaking, airlines will routinely operate flights with less than 100% water uplift. For a short haul quick turn, if the water quantity on a narrowbody aircraft was above 25%, no need to uplift extra water. For a long haul, sometimes the flight might be planned anywhere from 50% to 100% depending on the length of the route.

It is going to vary according to flight mission, passenger count, season, or what part of the world the flight takes place.
Here are the capacities from a company document.
MD88/90 47USG (177.9L)
MD11 250USG (946.4L) Estimated

732/733 40USG (151.2L)
737 60USG (226.8L)
747 3x 110USG = 330USG
757 66USG (249.8L)-Fill valve closes automatically at 50USG (189.3L)
762/763 120USG (453.6L)-Fill valve closes automatically at 102USG (385.5L)
763ER 160USG (600.6L)
764ER 224USG (847.9L)
772ER 300USG (1135.6L)

CRJ 200/700 31.5USG (galley 8USG/30L, lavatory 5USG/19L, toilet 18.5USG/70L)

As mentioned, the term "potable" water seems to be a minor overstatement. Some companies warn employees to not uplift any potable water overseas (which means not outside the US, Canada, or UK). But based on what I've heard, I wouldn't drink it wherever it came from.
Why You Should Think Twice Before Drinking Tap Water
Why you should never drink water on a plane, according to a flight attendant
Airline's drinking water fails hygiene tests
The "potable" water is usually chlorinated water, but you´ll never know about the truck or tank service overseas. Usually the galleys contain an anti-biological filter (silver ions) for the taps and coffee makers, which get changed regularly. Also the tanks will be disinfected every few weeks, normally during an A-check. Part of a C-check is to remove and test them.
On a B737, the potable water tank is in the aft cargo pit behind the last wall under the aft galley just right in front of the pressurized bulkhead. The tank itself is made out of composite materials and fiberglass. The tank is about 4 feet long and 2 feet tall. The 737s only have one potable water tank.
The B747 has three 110 gallon filament-wound fiberglass tanks attached to the forward side of the center section front spar (rear bulkhead of the forward baggage compartment). The water is moved from the tanks by pressurized air. This pressure is provided by electrically driven air compressors mounted next to the tanks. Not all operators use all three tanks and some have deleted some tanks. 747 AMM, 38-11-00, page 1, pg 2.
Passenger MD-11 hold up to four 63USG tanks, the freighter usually has all removed except for one. This water also serves for flushing the vacuum toilets if installed. The tanks sit in the utility tunnels (behind the sidewall) of the forward cargo compartment.

I wonder how many the Emirates A380s with the first-class showers have.

I used to work with the B747-400 when I was with Lufthansa. From what I can remember it had water tanks which could hold 1500kgs of water. On a long-haul flight from KUL to FRA we would generally uplift 75% so that would be 1125kgs. The selector for water quantity is on the panel next to the door 2L.
On water-source. We were required to get an external laboratory to do a water test. This involved bringing a technician to the water source at the airside where he would take a sample from each outlet and each water truck. The lab report was relayed to HQ.
When we stopped passenger flights to KUL, we still had freighters operating to KUL but these planes usually did not require water so we did not keep up our status as a water re-supply station. On one occasion a plane came in with empty water tanks and the outgoing crew insisted on uplift of water. This was not permitted because if any water from a 'non-certified' source was uplifted the tanks would need to be flushed and chemically treated when it went back to FRA base. In this case we loaded a few cartons of mineral water and the crew was happy.
Anilv

It depends. Airlines have an office that is constantly looking for ways to reduce weight as every pound of reduction can save thousands in fuel costs over the year.
When it comes to water (and pretty much everything else that's not mandated) they look at historical use by route, season, load factors, and service locations to predict needed quantities and set the amount to be loaded. The goal is to carry enough with a small margin over the predicted maximum need.


text:
What does "zero offset between two waypoints" mean in ICAO Doc 4444?
My question is with reference to the GNSS based separation specified in ICAO Doc 4444. Could someone explain the significance/meaning of the condition "zero offset between two waypoints" criteria?
if an aircraft had deviated, say due to weather, but is able to proceed direct to a particular waypoint, can the GNSS based separation still be applied with respect to another aircraft if we are able to establish that the two GNSS tracks are 15-135 degrees apart (but not on route)? It is this context, that I wanted to know the significance of "zero offset" clause.

Provide a link to where this is stated to give us all context.


text:
At what altitude do pilots usually switch to departure?
I contribute to an open-source ATC sim, and I'm looking to advance one of our current features. I know this is widely variable, but is there a typical example, either in distance from the airport, or altitude, that I can use to approximate when a pilot would switch to departure?
If you can give me an example of both so I can say "when N123AB climbs through altitude x OR is y miles from the airfield N123AB will contact departure". This would provide some more variation since we have a LOT of different aircraft types in the sim and they've all got different performance. Rates of climb and speeds would have a big impact here. This will be better than saying "after x amount of time N123AB contacts departure". Thanks for your help!

There is no typical altitude or distance. There are too many variables.

Generally a little bit before you exit class D airspace.

What is the open-source ATC sim please? Sounds interesting.

There is no standardized altitude rule for switching frequencies. This is done at the request of your current controller. If the airport is uncontrolled but you need to switch to a nearby ATC frequency for departure through controlled airspace you do so when you feel you are ready and/or when the local charts state you should do so because of airspace restrictions or other rules.

Indeed, if you're flying a small plane, you may never get to the altitude at which that commercial jet switches frequencies.  It's really up to the controller, and seems to have more to do with being clear of the airspace departing traffic would use.  E.g. in a small plane I might make a turn at about 1000 ft AGL, then be told to switch to departure, while that 737 following me departs straight out until reaching 10K ft or so, and doesn't switch to departure until later.

It will be different at every airport and even at different times for the same airport, but if you’re looking for a simple rule to keep things reasonably realistic, I’d go with 1000-1500ft AGL; that’s seems to be when I usually hear it.
If you want to make it annoyingly realistic, I’d say about 20-30 seconds at current climb rate before hitting the initial altitude in the clearance. I pretty consistently check in with Departure and get my next climb just as I’m leveling off.
Note that in some countries, your clearance will tell you to switch on your own when passing some altitude (MSL) rather than being told to by tower, and that’s typically 1000-1500ft AGL as well.

At least in central Europe, TWR at bigger airports will typically tell you "when airborne contact Departure" as a part of the takeoff clearance, which means you are supposed to do it as soon as practical (steady climb, gear up, …). TWR doesn't expect to talk to you again (unless your takeoff goes wrong).

There are two basic scenarios: On some instrument departure routes /SIDs, it is required to stay with the airfield tower controller until after passing a pre-defined fix or until being handed over. When that is not defined, one usually switches over a soon as stabilised in climb with a clean airplane and on track (aviate, navigate, communicate). Usually about 1000-2000 ft AGL. It also does not make sense to switch very early in flight, as sometimes the area controllers do not have radio reception / radar contact with the plane as it is still too close to the ground.


text:
Does the FAA require a specific grade of supplemental oxygen for part 91 operations?
In a recent FAA knowledge exam, a question was asked whether medical grade or industrial grade oxygen can be substituted for the aviation grade supplemental oxygen for General Aviation, Part 91 flight. I have looked in the FAR/AIM for answers. But, there is not a specific regulation prohibiting the use of medical grade oxygen in aviation.
The FAA Safety Brochure OK-09-439 recommends that medical grade oxygen should not be used. Yet, there is a Civil Air Patrol document (another government entity that is regulated in part by the FAA) that refutes this due to changes in the understanding and delivery of supplemental medical grade oxygen.
Does anyone have a clear cut and recent regulation or document that clarifies this question? Please include links to the documentation.

The only other document that I am aware of is The Pilots Handbook of Aeronautical Knowledge. "b. Differences between and identification of “aviator’s breathing oxygen” and other types of oxygen
The containers should be supplied with oxygen that meets or exceeds SAE AS8010 (as revised), Aviator’s Breathing Oxygen Purity Standard. To assure safety, periodic inspection and servicing of the oxygen system should be performed." There is also a mil spec  MIL-PRF-27210G but I can’t find a copy right now.

@JScarry - Thanks for that ref. SAE AS8010 gives the standard by which breathing gases can be classified as ABO. SAE International in their documentation states that they can not regulate or give standards for medical breathing gases because, “Medical oxygen is not covered by this standard. In the United States, medical oxygen is a prescription drug and complies with the United States Pharmacopoeia (USP). In Europe, medical oxygen specification compiles with the European Pharmacopoeia monograph (Ph Eur 0417).” But, it does not state that ABO is required. Just that the O2 must exceed standards.

Regulations don't usually include detailed technical requirements or specifications, but AC61-107B - Aircraft Operations at Altitudes Above 25,000 Feet Mean Sea Level or Mach Numbers Greater Than .75 / with Change 1 says (p. 33, emphasis in the original):

Only oxygen that meets or exceeds the Society of Automotive Engineers
(SAE) International Aerospace Standard AS8010 (as revised), Aviator’s
Breathing Oxygen Purity Standard, should be used.


text:
Why do flight attendants wear gloves during takeoff and landing?
Last time I was flying the flight attendant put on black leather gloves during while she was seated during takeoff and landing. She took them of as soon as she got up from the seat.
This wasn't the first time I've seen this.
Is this a safety of flight issue?
Edit:
The airline I've seen this was Finnair.
There where three flight attendants on the flight, but only one was sitting near me, so I couldn't see what the others did.

She was cold? I've never seen this happen and I fly a lot.

@RonBeyer: If she was just cold, why would she put off the gloves as soon as she got up?

Because she's got something to do where wearing gloves is a hindrance, for example.

Company rules may allow her to wear gloves while seated but not while performing duties. Airlines have some pretty strict dress codes

It might be helpful if you specified the airline(s) where you've seen this. As mentioned it may be something to do with specific company policies. Also, was it one of many attendants or all of them?

@FreeMan: I've added the information to the question.

Did they look something like what this Attendant has on? https://s-media-cache-ak0.pinimg.com/originals/43/8f/b5/438fb50cc551d9cd542a358be6df9db7.jpg

Flying tactical jets with the US Navy we were required to fly with Nomex gloves while flying ashore. In an accident, such as a crash during landing, if the hands get severely burned they will become useless making survival more difficult. They had leather palms and pilots complained that they became slippery if they found themselves in the drink, and would compromise safety in that environment. Pilots were encouraged to wear their gloves over water, but it was not required. They limited tactile sensation with the controls, and this made them undesirable from a routine operational perspective.

I don't see how this is off-topic. Flight attendants are required crewmembers and are subject to regulations just like any other crewmember. This question is just as much on-topic as asking why any other crewmember would do something.

Makes perfect sense to me. During takeoff and landing is when the cabin crew would have to be prepared for quick response to a fire and/or evacuation scenario; gloves could be useful/essential personal protective equipment in such a scenario.

From Finnair's Facebook page, it looks like Flight Attendancts wear gloves for safety reasons during takeoff/landing and galley preparation. Also it seems they do remove them when greeting passengers.

https://m.facebook.com/Finnair/posts/10151523242117911


text:
Why doesn't the 747 that is testing the GE9X have winglets?
Why doesn't the 747 that is testing the GE9X have winglets? The news says it is a 747-400, but it doesn't have winglets.

Good question. The same aircraft with JAL in 2010 has the winglets. They’re still there while it was stored at KVCV in Feb. 2011 before it was sold to GE. There’s an article here describing modifications made to the aircraft to accommodate testing. It doesn’t mention winglets but it does mention modifying the wing structure

That's because its been removed for testing. The aircraft used in for flight testing the GE-9X belongs to GE and is a modified JAL 747-400.

The aircraft, a former Japan Airlines -400, was acquired by GE in 2010 and
  following maintenance and interior modification in Xiamen, China,
  by Taikoo Aircraft Engineering, was delivered to Evergreen Aviation
  Technologies in Taiwan for installation of data racks and instrumentation.

For carrying out the testing, GE has carried out a number of modifications for maintenance and testing:

... modifications are also planned to reduce the chances of aero
  elastic interaction between the extended wing of the 747-400 and the
  GE9X mounted on the inboard left strut. GE has already removed
  the standard winglets because these add unnecessary weight and a
  maintenance burden to the aircraft’s flight-test role. Later this year,
  the outer 6 feet of each wingtip also will be removed, ... Designers say the stiffer wing will reduce potential exposure to limit cycle oscillation and maintain an unrestricted test envelope.

Quotes from archive.org. Original ariticle appears to be from aviationweek.

The winglets were also removed from the 747-400 Dreamlifter due to vibrations encountered during flight. citation

To quote from this article in Popular Mechanics,

In preparation for the flight, GE removed six-foot wing extensions from the 747 to reduce the wingspan to just over 195 feet, stiffening the wing to support the weight of the giant engine.

i.e. the 9X engine is heavier than the CF6 that is was replacing.  Therefore the wing needs to be stiffer.  If the wing was not stiffer, then the natural frequency would drop due to the heavier engine, and there may be a wing flutter concern.  The wing is basically a big beam, and shorter beams are stiffer than longer beams.


text:
How should a glider pilot handle inadvertently entering a foreign country?
Typically, when an aircraft lands on a different country than its departure, it has to land on an international airport. There many services are provided like customs, passport control etc, to make the entrance to the country legal.
But what happens on an unpowered aircraft? (i.e. sailplane, paraglider, hangglider etc).
These aircraft may be forced to cross a border and not be able to return but to the country of origin. Landing at an airport (let alone international), may not be possible. As an example consider a paraglider that is blown back to the lee side of a mountain.
These aircraft usually don't file a flight plan, they are not equipped with a transponder, may not have radios to communicate with ATC, and possibly may not be detected by radars.
How can the pilot make their arrival formal, their stay legal and eventually return to the origin country with out problems? Is there any law protecting pilots in such cases, or will they be treated as illegal immigrants?
In general, if this ever happen to someone, what is the first action they have to take, and who shall they contact?
Consider crossing an "unfriendly" border. A EU citizen getting from an EU country to another obviously will not have any problems. But visiting a country that a visa is needed, or that in general you are not allowed entrance seems more troublesome.

I vote to close.  This is about border policies, not aviation.

@MichaelHall Disagree. This is about flight planning.

If one is that close to a border, one better be equipped to address the situation - like having a radio on board at a minimum.

@MichaelHall I am not asking how to just enter a foreign country, this is not about border policy. I am asking how a pilot should handle the situation where they inadvertently (and are probably forced to) enter a foreign country.

@J. Hougaard – I would agree with you if the OP asked about how to avoid crossing an international border in a glider.  Instead, he asked what to do AFTER you get there.  The method of arrival is actually secondary in this case.

@user3634713 – I understand exactly what you are asking.  As I mention above, the method of arrival isn’t critical to your question of how to handle things once you have arrived.  As you acknowledge in the question, the laws will vary by country so there is no good answer.  Your origin country’s diplomatic relations, “host” country’s immigration law, and the current geo-political environment will all come into play.  EU maybe not a big deal.  North Korea?  You are going to prison for a while.  My point is that there isn’t an aviation specific answer here…

It's not remotely correct to say "when an aircraft lands on a different country than its departure, it has to land on an international airport".

If you inadvertently cross the border, then you should call the local authorities right away. Ideally from your phone, while staying exactly at the place of landing. Less ideally, hitchhiking a trip to local police. You will be arrested for illegal crossing and spend time in jail followed by a fine, but that is nothing compared with you getting caught.
Illegal crossing is a serious offence and even if you are sure you could cross back safely and never end up in the same predicament, is still advisable to report to local authorities.


text:
Are CVR and FDR reset after every flight?
Recording the thousands of parameters and voice conversations must take a huge amount of storage, and so I am wondering, how frequently is this data "deleted", so it can be used again?
For example, after every successful flight, is the CVR and FDR data deleted or it records maybe 10 flights or so, and then is reset?

This seems useful: https://www.quora.com/What-is-the-memory-capacity-of-a-flight-data-recorder-and-cockpit-voice-recorder

Related

They record on a "loop" so that the oldest data is automatically overwritten by the latest data.  The number of flights depends on how long each flight is, and sometimes is only part of one flight.  As far as how long, there are different rules for different aircraft, and probably different rules for different countries.  Do you have a specific set of regulations that you are asking about (US/FAA, Eurpoe/EASA, or somewhere else)?

No, they are not reset after each flight, but as commented, the FDR and CVR are on a loop, and just keep recording over the old data. For US registered aircraft, FAA Regulation "14 CFR 91.609" covers flight data recorders and cockpit voice recorders.
It states for flight data recorders:

(c) 1. No person may operate a U.S. civil registered, multiengine, turbine-powered airplane or rotorcraft having a passenger seating configuration... of 10 or more that has been manufactured after October 11, 1991, unless it is equipped with one or more approved flight recorders that .... are capable of retaining no less than 8 hours of aircraft operation.

And:

(c) 3. All airplanes and rotorcraft subject to (the above)... manufactured on or after April 7, 2010, must ... retain at least the last 25 hours of recorded information...

For cockpit voice recorders:

(h) 2.  All airplanes required by this section to have a cockpit voice recorder and a flight data recorder, that are manufactured before April 7, 2010, must by April 7, 2012, have a cockpit voice recorder that also ... retains at least the last 2 hours of recorded information ...

There are not "thousands" of parameters.
The CVR must record the following 25.1457 (Cockpit voice recorders):

(1) Voice communications transmitted from or received in the airplane by radio.
  (2) Voice communications of flight crewmembers on the flight deck.
  (3) Voice communications of flight crewmembers on the flight deck, using the airplane's interphone system.
  (4) Voice or audio signals identifying navigation or approach aids introduced into a headset or speaker.
  (5) Voice communications of flight crewmembers using the passenger loudspeaker system
  (6) all datalink communications

So, probably 6 or so channels.
For the FDR, wikipedia states "There are 88 parameters required as a minimum under current US federal regulations (only 29 were required until 2002), but some systems monitor many more variables."
So, if the flight lasts less than two hours, there will be at least the whole flight on the CVR. But if the flight is longer than two hours, you only have the last two hours.

I recall seeing at least some flight deck photos showing a CVR erase switch, allowing the crew to erase what's on the cockpit voice recorder. Maybe you can comment on that?

The standard (EUROCAE ED-112) provide for a means to erase voice and video recordings following completion of a flight. Interlocks prevent erasure before the aircraft  has landed safely (on ground, engines off). Mostly political so that idle comments made in flight aren't used by the airline against the pilots. Not too likely though as the CVR has to be removed from the a/c before any recordings can be offloaded.

@Gerry You don't need to remove the CVR or FDR for a readout. You just need a laptop or special PDA. Readouts have to be done regularly by maintenance to ensure they are operational.

FDRs are not required to record thousands of parameters.  However, some FDRs (especially newer ones installed in newer aircraft) do record thousands of parameters, in the name of air safety.


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How expensive would it be for ejection seats to be installed on commuter planes?
Statistically, the chances of you being in an aircraft incident are extremely low, and once these seats are in place, you would never have to move them or do maintenance.
The only difficult task is redesigning the fuselage to support ejection, I assume.
Has this ever been discussed, and if so, is there any action being taken on it?

The only difficult task is redesigning the fuselage to support ejection, I assume. if that was true, don't you think this would've been done already?

Redesigning the fuselage to support ejection is, itself, a gigantic undertaking, with huge safety impacts. Passenger planes do not have canopies that can be quickly detached in case of emergency. Introducing such a feature, which would have to maintain pressure and cover most of the aircraft's roof, would be quite the design problem, and if it was possible at all, would introduce the risk of new kinds of failures that may very well risk more lives than the very few ejection seats could possibly save.

Also, citation needed for "you would never have to move them or do maintenance." Everything needs maintenance, and surely seats with explosives attached to them need careful maintenance indeed.

You are also going to have to do some thinking about how the ejection mechanism is going to be triggered.  If by the passenger, how do you stop them from ejecting accidentally (or on purpose, for suicide or thrills)?  Will the plane and all the non-ejected passengers survive an ejection?  If it's triggered by the pilot, how do you guarantee that everyone's in their seat, with arms & legs in the correct position? How about babies carried on parents' laps?  And suppose everyone - maybe 400+ people in a jumbo -  is ejected, what then?  400 tangled parachutes?

Are you including the problem of each passenger needing to also have a parachute in your question?  Have you ever been a passenger on a commuter aircraft?

You realize the ejection seats have rockets on them. I don't see being in a plane full of rockets as being safer than a plane not full of rockets.

Never do maintenance?? In air forces, there are special staff engineers who only perform maintenance on ejection seats (and other non-weapon explosives in the aircraft).

Ejection seats are heavy. Even if the seats had zero initial cost, the weight alone would probably double the cost of every airline ticket.
The flying public don’t want to pay for a couple of inches of leg room. They certainly won’t want to pay for a safety item that would probably never get used.

Aside from the weight and expense issues, consider that an ejection is a very dangerous thing to do... for example, the ACES 2 seat used in most US military aircraft has around an 85% success rate. The definition of success is, the person survived, quite possibly with injuries.
Current ejection technology requires the person to be tightly strapped into the seat with a full six point harness.
An ejection is a very violent event. You get slammed with 20G's when the rocket goes off. If you're not in top physical condition, as military pilots are, your spine will be damaged. If your head isn't held perfectly inline with your spine, your neck will be fractured. If your arms or legs strike any part of the aircraft on the way out, they will be ripped off. And you still have to make a parachute landing, where you hit the ground at about the same speed as jumping off of a fifteen foot ladder. Many military pilots report a loss of one half to one inch of height after an ejection, due to compression of the spine.
And freaky things can still happen. When Chuck Yeager ejected from an out of control NF104, he separated from the seat, and then slammed into the bottom of the seat, where the burning residue from the rocket motor set his flight helmet on fire. When an SR71 was lost while trying to launch a D21 drone, the RSO (back seater) died when he landed in the ocean and drowned.
So, imagine the average civilian, blasted out of an airliner. Their neck is fractured, they probably lost an arm or a leg on the way out, they slam into the ground and fracture their pelvis, and the parachute catches the wind and drags them across the ground for some distance... if they survive all of that, they'll die from their injuries before rescue teams can arrive.
Ejection is a measure of last resort in a military aircraft that can be expected to suffer battle damage, for a military pilot in top physical condition, tightly strapped in, and trained on what to do, when it's either maybe get killed or definitely get killed if you don't eject.
For the average civilian, in the safest form of mass transit, it would just be a different way to die.

The proof of the pudding would be: Do military transport planes (say, C130 Hercules) have ejection seats for the pilots? No, they do not. So even the pilots who can be assumed to stay in their seats as opposed to the average passenger don't get one; and forget about those drunks going to or returning sunburnt from party destinations.  What will you do when walking through the aisle when suddenly all 555 chairs around you explode out of the roof? What will you do on a 2-layer A380 (or even a 747 jumbo), crash the lower layer through the top layer?


text:
What is a GDS (in the context of the airline industry)?
I have been looking at this article and throughout the article they mention GDS's but do not explain the terminology. Does somebody know what they are talking about -
For e.g. -

Three GDSs emerge from the previous CRSs and sold off by airlines;
  pricing transparency grows - centerforaviation.com

CRS I am assuming/presumng means Computer Reservation System.

NOT OFF TOPIC!  If you follow the airline industry, this term comes up frequently, and to understand the conomics behind this part of modern aviation,  you have to understand what a GDS is. VTLO.

GDS stands for Global Distribution System:

A Global Distribution System (GDS) is a network operated by a company
  that enables automated transactions between travel service providers
  (mainly airlines, hotels and car rental companies) and travel
  agencies. Travel agencies traditionally relied on GDS for services,
  products & rates in order to provision travel-related services to the
  end consumers. A GDS can link services, rates and bookings
  consolidating products and services across all three travel sectors:
  i.e., airline reservations, hotel reservations, car rentals.

These are the databases that maintain travel reservations and allow travel agents to see available inventory and book tickets. As noted in the Wikipedia article, they may also host airlines' computer reservations systems and passenger service systems. For example, Amadeus operates a system used by hundreds of airlines, not to mention thousands of hotels, rental car companies, tour operators, and other travel businesses to maintain reservations and track inventory, and a global distribution system used by tens of thousands of travel agencies, ranging from storefronts to online booking websites, that allows agents to book travel with these providers.


text:
Why must some 'dangerous items' be in check-in baggage?
What is the rationale behind forcing passengers to check in dangerous items?
What makes liquids and gels more dangerous in the cabin? Why would a lithium ion battery be less dangerous as check-in luggage? Wouldn't that even be more dangerous when you put lots of batteries in the cabin, since one could catch fire and spread to all other batteries where passengers are?

Relevant XKCD

Generally, "dangerous" things that might be used as weapons are required to be kept out of the cabin. For instance, you can have firearms in checked baggage, but not carried in the cabin.
Given what's been learned about terrorist planning, there were plots to bring liquids on board an aircraft that could be combined to form an explosive. To counter that threat, the amounts & types of liquids that can be brought on board have been limited. Since the liquids in isolation are safe, they're allowed in normal quantities in checked luggage.
In the case of Lithium Ion batteries, the concern is less their use as a weapon, and more about a defective battery catching fire. If this were to happen in a cargo hold, the fire would cause other things to start burning as well before the cargo smoke detectors alert the crew to what's going on. So the priority is to keep lithium ion batteries out of the cargo hold. They're allowed in the cabin (with some restrictions) since you're pretty likely to notice your cell phone getting hot & smoking if it's in your pocket, and with that sort of early notice, the fire can be dealt with before it's caught large volumes of material on fire as well.
At least that's the theory. I don't know how many times it's been put to the test. In at least two cases (the Samsung Note 7 phone, and hover boards), devices which are considered to be at high risk of catching fire are simply kept off the aircraft altogether.

Can we get a citation on the liquid aspect? That seems pretty unbelievable that liquids mixed by a person are a threat, and liquids mixed by some Macguyvered mechanism would not be a threat.

@Scott You have more faith in the TSA's rationality than I have. https://www.theatlantic.com/national/archive/2014/01/tsa-business-security-theater-not-security/357599/ https://www.schneier.com/essays/archives/2009/11/beyond_security_thea.html

There's been a recent case of some dude biting into an iPhone battery and making quite a mess on the Internet, if I remember correctly. Hopefully terrorists on airplanes won't learn that trick.

@Scott "liquids mixed by some Macguyvered mechanism would not be a threat" Presumably the idea is that scanning of hold-baggage would spot anything more suspicious than completely separate containers.

@scott in the TSA's own words:  https://www.tsa.gov/blog/2008/02/04/more-liquid-rules-why-we-do-things-we-do-commenting-disabled (which doesn't really answer the question, though); a better explanation at https://science.howstuffworks.com/liquid-explosives.htm describes several combinations of relatively safe chemicals that can be mixed into an explosive.  Fox News even describes how Tang drink mix and the hydrogen peroxide from your medicine cabinet can make a bomb. http://www.foxnews.com/story/2008/05/17/tang-bomb-liquid-explosives-are-new-weapon-choice.html

@Scott There are lots of liquids that, if mixed, are explosive or incendiary. A basic chemistry class should resolve any disbelief of that. As for the MacGyvered mechanism in hold baggage, hold baggage is x-ray screened and (at least in the U.S.) also tested for explosives, so the idea is that they'd catch that in screening and not let the bag on the plane. For carry-on baggage, someone could take their bag into a lav (or a first class suite, etc.) and combine the chemicals manually, so there would be no MacGyvered mechanism for security to detect.

The term for the liquid mixable explosives is binary explosives.

I believe there was a letter to the TSA signed by quite a few Nobel laureates in chemistry that the idea of a liquid binary explosive being a danger to a plane was not based on any known science. In other words, Security Theater.

The fire danger is even more important for lithium-metal batteries (such as the little coin-shaped ones in computer motherboards) than for lithium-ion and lithium-polymer batteries, since burning lithium-metal batteries are essentially impossible to extinguish; the only thing that can be done is to isolate it from other combustibles before it ignites anything else and keep it isolated until it burns itself out, which is much easier to do in the passenger cabin than in the cargo hold.  This is the reason lithium-metal batteries are completely banned from any sort of air transport...

... except for those installed in personal electronic devices (laptops, for instance) plus up to one spare battery per device, all of which must be in carryon rather than checked baggage.

Why is the rationale of forcing passengers to check-in dangerous items?

To stop people using them as weapons to hijack the plane.

What makes liquids and gels more dangerous in the cabin?

There was a terrorist plot in which suicide bombers would blow up planes using liquid explosives disguised as soft drinks. Of course, somebody could try to put such a bomb in checked luggage but that would require some sort of timer and detonator, which would likely be spotted when the luggage is X-rayed. So the specific concern is that a bomb could be assembled and detonated in the cabin using only innocent-looking liquids and other items.

Why would a li-ion battery be less dangerous as check-in luggage? Wouldn't that even be more dangerous when you put lots of batteries in the cabin, since one could catch fire and spread to all other batteries where passengers are?

Lithium batteries are more dangerous in check-in luggage.
How would the fire spread between batteries in the passenger compartment, unless the whole cabin is on fire? Your laptop isn't suddenly going to start burning just because my cell phone has caught fire in the seat next to you.
If a battery fire starts in the cabin, somebody will notice before it sets much else on fire. They can then put the fire out. The standard technique, I believe, is to drop it in a bucket of water, which removes all the heat from the system, as well as starving it of oxygen. Everybody lives to tell the tale.
In contrast, if a battery fire starts in the cargo hold, it's in an area that's densely packed with flammable things such as clothing. That means that, by the time the fire is detected, it is probably quite big. Further, the only way to fight such a fire is with a general fire suppression system that tries to starve the entire hold of oxygen. That doesn't remove the heat so, even if it puts the fire out, it's possible that the still overheated battery will reignite the fire. This is an extremely dangerous situation that could well kill everybody.

I don't believe the standard technique for a battery fire is to drop it in a bucket of water. Do they have buckets big enough for a laptop at all? They'll use a class D-rated fire suppression agent, which would work both on a lithium primary and a lithium-ion fire.

@QuoraFeans Probably not for a laptop. But for phones, I think that's the procedure.

Notice that this approach might work for some types of lithium based batteries, but not all. And it's not always possible to know what type of battery you have at hand.

@QuoraFeans -- Li-Ions always are suppressed using water to quench the runaway reaction.  Class D agents can be actively harmful due to the fact that a burning Li-Ion battery has oxygenated fuels and decomposing cathode oxide (producing oxygen) in it already, so it doesn't need all that much air to burn or propagate the runaway to adjacent cells.

does water even work for Li-ion batteries (in terms of the battery not burning anymore), or does it work solely to contain the damage?

@JohnDvorak It's got a huge specific heat capacity so it stops the thermal runaway, as well as absorbing the damage.

Regarding lithium-based batteries, Why is there so much fear surrounding LiPo batteries? on [electronics.se] may be of interest.

Wait, they drop lithium batteries in water? That just sounds like a bad idea.

@reirab if you don't drop it in water, it does this. I know which I prefer! The water absorbs the heat and contains the reaction. The resulting lithium hydroxide solution is presumably rather dilute so not very dangerous.

@reirab So you have a choice between "releases toxic fumes and stays nicely contained in a water bucket" or "releases toxic fumes and also catches everything else on fire". Pick one

@immibis It was more of the "alkaili metals react violently with water" part that was my primary concern than the release of toxic fumes. Accidentally combining lithium and water is how meth manufacturers who failed chemistry regularly blow themselves up. Perhaps a large enough bucket of water would be sufficient to contain the resulting explosion from the quantity of lithium in a small battery, though.

@reirab I think containing the energy is the point (water has an unusually large ability to absorb heat), along with the fact that you have an alkali metal fire either way.

@reirab, lithium doesn't explode when mixed with water.  Lithium produces hydrogen and heat when mixed with water, and it's the hot hydrogen that explodes.  Drop your lithium in enough water, and you get cold hydrogen that never builds up to explosive levels.


text:
Do pilots of modern aircrafts still use maps, gps and compasses to find airports?
Do pilots of modern aircraft still need to navigate using maps, GPS and compasses to find airports?
Alternatively do they use some sort of fully automated system that navigates the aircraft via auto pilot to the airport, so you simply key in the GPS co-ordinates and it takes you there, or even better, you just type the name of the airport?
This is similar to this question that was closed as being too broad.

What do you consider the alternative to a GPS to be?

I do not know of any systems anymore that still require "co-ordinates".  Everything from the lowest end GPS will use Airport Identifiers and Waypoint Names.

The preferred method of navigation on anything newer than a "six-pack" is a "Moving Map GPS", that shows the position and course of the aircraft on a map of the environment, including airspaces, airports, waypoints, and major landmarks.   Many systems also show terrain, weather, and other air traffic.
Route planning is done by entering the origin, destination, and any waypoints along the way. There are however instances where plain coordinates are used, such as in oceanic flights.
When the GPS is coupled to an Autopilot, the autopilot can fly virtually the entire route other than takeoff and landing. But pilots must always be monitoring to address ATC instructions, weather, traffic or other issues.
GPS can occasionally have disruptions, so most pilots keep paper maps handy, and cockpits have a magnetic compass.  Pilots should be prepared to navigate with nothing more than a map, compass and stopwatch if the need arises.


text:
How much fuel gets dumped and why?
WRT Would the Aeroflot Flight 1492 have been able to dump its fuel first before landing?, I am wondering how much fuel gets dumped every year? gallons? litres? pounds?
Also, is it only in unplanned or emergency situations?

Why would anyone plan to dump fuel?

Most shorthaul aircraft do not have the capability to dump fuel.

Only in emergencies.  It'll be a pretty small number.  You might find something like a study on the IATA web site.  It doesn't effect people on the ground because the fuel evaporates pretty quickly.

While according to British Airways estimates quoted in the Inter-Governmental Panel on Climate Change (IPPC) report on “Aviation and the Global Atmosphere” published in 1999 “only a very small percentage (on the order of 0.01%) of fuel used by the aviation industry each year is jettisoned”
https://greentumble.com/environmental-impacts-of-fuel-dumping/


text:
Does anyone know what this set of aviation wings signifies?
I stumbled upon this set of aviation wings whilst searching through a box of old things, though I'm at a loss as to their origin, and what they symbolise.
Judging from the lack of skill used to craft the item (Seems the mold had an off day), I doubt it's rare, though I could, very likely, be wrong.
Other than what you can see in the picture, the wings are roughly two inches long, and made of metal; sterling silver, perhaps?
As for background information, I did have Polish family who fought during WW2 in the west, and another who served in the RAF Regiment. There really isn't much else I can tell you, so I apologise for the ambiguity.
Still, I hope you can help!

Asked in the History exchange, and added a clearer image.

Looks like German eagle for me

no, please don't ask the same question on two sites at the same time!

@Notts90 not necessarily, in Italy signifies "military" vs "civilian" eagle

What material is the blue part on the back?


text:
What does "leave clear on its left" mean in UK regulations relating to collision avoidance on non-runway landings?
This doesn't seem to be plain English, could someone explain this with a simple example for me please? I'm not sure what 'Leave clear on it's left' means, and it's not clear whether the subject of the sentence is 'A flying machine [etc.]' or 'An aircraft that has landed' (i.e. who's left are we talking about)

Landing and take-off
(2) If take-offs and landings are not confined to a runway—
(a) when landing, a flying machine or glider must leave clear on its
  left any aircraft which has landed, is already landing or is about to
  take off;
(b) a flying machine or glider which is about to turn must
  turn to the left if the commander of the aircraft is satisfied that
  such action will not interfere with other traffic movements; and
(c) a
  flying machine which is about to take off must take up position and
  manoeuvre in such a way as to leave clear on its left any aircraft
  which has already taken off or is about to take off.

(CAA:"The Rules of the Air Regulations 2015 ")
I've tried searching for the term online but only seem to be able to find excerpts from the legislation.

Pass to your right?

@MikeBrass How can I pass to my right?  Surely I pass to their right?  Or is that their left?  ....  Either way there's at least 50% chance you're right.

0Keep the impeding aircraft on your left, immaterial if it is pointind towards you or awal from you - thus passing to your right.

@MikeBrass is that a guess or is this the standard accepted interpretation of that rule?

An assumption, you can call it a guess.  It places the traffic on the pilot's left- where he has a window to better observe.

Seems understandable to me.
It may be more clear with commas...
"(a) when landing, a flying machine or glider must leave clear, on its left, any aircraft which has landed, is already landing or is about to take off;"
Basically leave enough room between you and any aircraft which may be on your left as you pass them.
The grammar may be a little dated but still perfectly accurate.

Welcome to Aviation.SE! A good first answer, if you haven’t already done so, please check out the [help] to see how the site works.

It's a little more than "leave enough room between you and any aircraft which may be on your left". If there is an aircraft ahead of you, you must stay to (your) right of it.

If there is an aircraft ahead of you, you should never have landed!

@user33214 Land After clearance?

Not even after a clearance. Unless you want this on your gravestone "The controller said it was ok.".
ATC clearance gives the commander of the aircraft permission to land. It is still up to the commander to take the final decision on whether it is safe to do so.

@user33214 My point was that in the UK you can be given a Land After clearance, and it isn't unusual to actually land on a runway before the preceeding aircraft has vacated.  There are conditions - daylight, sufficient separation, the landing aircraft can see the aircraft ahead etc. Obviously if you don't think it is safe you don't do it, but to say that 'If there is an aircraft ahead of you, you should never have landed!' isn't always true